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In the case of a suspected radionuclide contamination of an area, it is essential to be able to estimate the background to determine if additional contamination is present. Precipitation has been used successfully to estimate fallout deposition, e.g. for Cs-137 in AMAP. A more detailed description of the relationship between precipitation and Cs-137 fallout deposition was presented and validated in a published study in Iceland which showed much better correlation between deposition and precipitation than seen previously. The concentration of the radionuclide in precipitation is the key factor linking precipitation and deposition. Best deposition estimates are obtained if concentration and precipitation time series are available.
Concentration time series for Cs-137 and Sr-90 have been compared between different locations in the Nordic countries and the UK as a part of the NKS-B EcoDoses and PardNor activities. This showed that the concentration can generally be represented by the same time series for all locations in the region, for a given radionuclide. The study is currently being expanded to include global data and results show that it is possible to describe the concentration time series with a relatively simple function, depending on region, radionuclide and possibly other factors.
The aim with DepEstimates is to:
· Validate the concentration time series function derived using global data sets with Nordic data
· Expand the function to include Pu isotopes
· Validate the method of estimating Pu fallout deposition from precipitation data, taking also other sources of Pu deposition into account, such as the Chernobyl accident.
· Present results to Nordic authorities and as a paper in a scientific publication
The main work would be within (c). Risř and STUK have been studying Pu in the environment for decades and have good data sets for validation. Pu would be analysed in the same soil samples from Iceland as have previously shown high correlation between Cs-137 deposition and precipitation. A seminar on results planned and the final results would be presented in particular to relevant authorities. | 
